Optimization of integrated circuit reliability

ABSTRACT

A per-chip equivalent oxide thickness (EOT) circuit sensor resides in an integrated circuit. The per-chip EOT circuit sensor determines electrical characteristics of the integrated circuit. The measured electrical characteristics include leakage current. The determined electrical characteristics are used to determine physical attributes of the integrated circuit. The physical attributes, including EOT, are used in a reliability model to predict per-chip failure rate.

FIELD OF THE INVENTION

The present invention relates generally to the field of integratedcircuits, and more particularly to predicting the reliability ofintegrated circuits.

BACKGROUND OF THE INVENTION

Integrated circuits are found in a wide variety of equipment, includinghousehold appliances, consumer electronics, communications systems,automotive systems, aircraft, and the like. As dependence on integratedcircuits has increased, the reliability of these devices hasincreasingly become an important concern. In general, as devices scaleto smaller silicon fabrication technologies, they often become lessreliable for the same use conditions.

There are many failure mechanisms that affect the reliability of anintegrated circuit. Several of these mechanisms are influenced by thegate oxide thickness of the integrated circuit, for example, BiasTemperature Instability (BTI) and Time Dependent Dielectric Breakdown(TDDB). Bias Temperature Instability can be either negative or positive,and relates to the change in threshold voltage and drain current with achange in gate oxide thickness of a metal-oxide-semiconductorfield-effect transistor (MOSFET) in an integrated circuit. TimeDependent Dielectric Breakdown is a failure mechanism in MOSFETs, whenthe gate oxide breaks down as a result of long-time application ofrelatively low electric field. The breakdown is caused by formation of aconducting path through the gate oxide to the substrate due to electrontunneling current, when MOSFETs are operated close to or beyond theirspecified operating voltages. Reliability models that rely on equivalentoxide thickness (EOT) based on a small sampling of production wafer kerfstructures do not account for the inherent process variability in thedeposition of the gate oxide layer across the wafer.

SUMMARY

Embodiments of the present invention disclose a method, computer programproduct, and structure for optimizing reliability of integratedcircuits. Several integrated circuit failure mechanisms depend on thethickness of the gate oxide. An equivalent oxide thickness (EOT) is adistance, usually given in nanometers, which indicates how thick asilicon oxide film would need to be to produce the same effect as thehigh-k (or high dielectric constant) material being used. If the EOT islow, or as the oxide thickness degrades with use of the integratedcircuit, reliability may be negatively impacted. In an embodiment of thepresent invention, a per-chip equivalent oxide thickness (EOT) circuitsensor resides in an integrated circuit. The per-chip EOT circuit sensordetermines electrical characteristics of the integrated circuit.Specifically, the per-chip EOT circuit sensor detects leakage currentthat occurs when a set voltage is applied through the integrated circuitgate. The determined electrical characteristics are used to determinephysical attributes of the integrated circuit. The detected leakagecurrent is inserted into an industry-standard algorithm, known asquantum mechanical direct tunneling current density as a function ofdielectric thickness at a fixed applied voltage, to calculate theper-chip EOT. The calculated EOT may be used in a plurality ofreliability models to predict the reliability of the chip for which theEOT was measured. The reliability modeling is optimized per-chip andthat chip may be placed in a suitable application.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating a semiconductortesting environment, in accordance with an embodiment of the presentinvention.

FIG. 2 is a flow diagram illustrating a qualification process for a newintegrated circuit technology and/or product, in accordance with anembodiment of the present invention.

FIG. 3 is a flowchart depicting operational steps of a reliabilityprogram, on a computing device within the semiconductor testingenvironment of FIG. 1, for predicting per chip reliability, inaccordance with an embodiment of the present invention.

FIG. 4 depicts a block diagram of components of the computing deviceexecuting the reliability program, in accordance with an embodiment ofthe present invention.

DETAILED DESCRIPTION

The embodiments of the invention and the various features andadvantageous details thereof are explained more fully with reference tothe non-limiting embodiments that are illustrated in the accompanyingdrawings and detailed in the following description. It should be notedthat the features illustrated in the drawings are not necessarily drawnto scale. Descriptions of well-known components and processingtechniques are omitted so as to not unnecessarily obscure theembodiments of the invention. The examples used herein are intendedmerely to facilitate an understanding of ways in which the embodimentsof the invention may be practiced and to further enable those of skillin the art to practice the embodiments of the invention. Accordingly,the examples should not be construed as limiting the scope of theembodiments of the invention.

For a given application condition, there is a growing gap between theexpected reliability targets of semiconductor products and the specifiedfunctionality of integrated circuits at nanometer technology nodes. Inorder to address these concerns, the embodiments herein provide astructure, computer program product and method to efficiently utilizedesign for reliability technology in integrated circuits by means of astandardized on-product service processor macro structure. Theembodiments herein utilize a memory mapped address to interface withapplication function in mission mode; store stimulus and signatures;integrate quality and reliability sensors; integrate various embeddedanalog and digital cores; execute test programs and test patterns; andutilize joint test action group (JTAG) and network input/output (I/O)connections.

Reliability is a design engineering discipline that applies scientificknowledge to assure a product will perform its intended function for therequired duration within a given environment. This includes designing inthe ability to maintain, test, and support the product throughout itstotal life cycle. Limitations of this discipline include high failure intime (FIT) rates; lengthy reliability evaluation; reliabilityengineering (RE) bridging scalability; defect detractors; and power andthermal control issues. The design and methodology presented herein,with enhanced-circuit limited reliability (CLR), utilizes VirtualQualification Platform (VQP); Embedded Quality Management (eQM); On-lineGlobal Reliability Model (OGRM); Embedded Reliability Engineering (RE)Evaluation; and Dynamic Product Grading (DPG).

Qualification testing of new integrated circuit technology consists ofexposing a number of integrated circuits to accelerated environmentaltests the simulate field conditions in order to verify the reliabilityof the new technology. Currently, reliability modeling for integratedcircuits, also referred to as chips, is largely based on qualificationtesting results of relatively small sample sizes. Variability of aspectsof the manufacturing processes over the life of the product may not betaken into account in the modeling since the small sample size used inthe qualification testing may not be representative of day to dayvariations that take place in manufacturing processes. Severalintegrated circuit failure mechanisms are dependent upon the gate oxidethickness. As is known to one skilled in the art, the gate oxide is thedielectric layer that separates the gate terminal of a MOSFET from theunderlying source and drain terminals as well as the conductive channelthat connects source and drain when the transistor is turned on. Gateoxide is formed by oxidizing the silicon of the channel to form a thininsulating layer of silicon dioxide. A conductive gate material issubsequently deposited over the gate oxide to form the transistor.Reliability predictions are made using the equivalent oxide thickness(EOT). An equivalent oxide thickness is a distance, usually given innanometers, which indicates how thick a silicon oxide film would need tobe to produce the same effect as the high-k (or high dielectricconstant) material being used. If the equivalent oxide thickness is low,or as the oxide thickness degrades with use of the integrated circuit,reliability may be negatively impacted. As known to one skilled in theart, wafer kerf structures are non-functional areas of the wafer,outside of the active integrated circuits. The equivalent oxidethicknesses used in reliability predictions are calculated from devicequalification test results and limited measurements from productionwafer kerf structures.

Embodiments of the present invention recognize the value of predictingreliability per chip as a way to determine the optimum operatingconditions per product. Embodiments of the present invention enable EOTmeasurements per chip, with one or more sensors per chip, each sensordetecting one EOT measurement, which can significantly reduce thevariability of the reliability prediction and optimize the modeling. Theability to characterize the reliability of each chip enables sorting ofthe chips by estimated field life. The most reliable chips may beinstalled in specific, high reliability systems to avoid system downtimeand to avoid unnecessary component replacement in the field.Implementation of embodiments of the invention may take a variety offorms, and exemplary implementation details are discussed subsequentlywith reference to the Figures.

The present invention will now be described in detail with reference tothe Figures. FIG. 1 is a functional block diagram illustrating asemiconductor testing environment, generally designated 100, inaccordance with one embodiment of the present invention. FIG. 1 providesonly an illustration of one implementation and does not imply anylimitations with regard to the various environments in which differentembodiments may be implemented. Many modifications to the depictedenvironment may be made. In the illustrated embodiment, semiconductortesting environment 100 includes computing device 102, semiconductordevice 104 and tester 106 interconnected via network 108. Semiconductordevice 104 may also be directly interconnected to tester 106.

Reliability modeling for integrated circuits is performed in one or moreof several different methods. In the preferred embodiment of the presentinvention, technology-specific sensors for measuring physical oxidethickness of the silicon active area, in addition to environmentalchip-specific sensors for measuring power-on-hours, temperature,activity factors and voltage are integrated into the design of each chipon a wafer. An external tester applies a set of test controls and testconditions across all the devices on the integrated circuit. The appliedvoltage causes a leakage current through the gate. Leakage current is agradual loss of energy from a charged capacitor. It is primarily causedby electronic devices attached to the capacitors, such as transistors ordiodes, which conduct a small amount of current even when they areturned off. Even though this off current is an order of magnitude lessthan the current through the device when it is on, the current stillslowly discharges the capacitor. Another contributor to leakage from acapacitor is from the undesired imperfection of some dielectricmaterials used in capacitors, also known as dielectric leakage.Dielectric leakage is a result of the dielectric material not being aperfect insulator and having some non-zero conductivity, allowing aleakage current to flow, slowly discharging the capacitor. The testerinterfaces with the integrated sensors and uses technology-specificequivalent oxide thickness (EOT) sensors to measure and characterizetunneling current density by device type as a function of physical oxidethickness. The tester interacts with the integrated technology-specificsensors via a Joint Test Action Group (JTAG) interface connected to ascalable parametric macro (SPM) which drives the control, data and powersignals required to independently isolate and/or operate the integratedtechnology-specific sensors. A reliability program residing on anexternal computing device, or on a device such as an embedded qualitymanagement (EQM) controller or on a tester, such as tester 106, insertsthe measured technology-specific EOT into a product-specific algorithmfor calculation of the failure rate of the integrated circuit that wastested. The reliability program inserts the EOT into one or morereliability models that predict integrated circuit reliability based onthe per-chip EOT, the manufacturing defect density, the test screens andthe application conditions. In general, the lower the EOT, the higherthe failure rate prediction is for the integrated circuit, depending onthe failure mechanism. Optimization of reliability modeling is achievedby using per-chip EOT measurements to predict product life forindividual integrated circuits including static random access memory(SRAM), embedded dynamic random access memory (EDRAM), ternary contentaddressable memory (TCAM), non-volatile random access memory (NVRAM),read only memory (ROM), electrically erasable programmable read onlymemory (EEPROM), cores, digital logic, and analog devices, instead ofrelying on EOT measurements made on a small sample of qualificationhardware or kerf structures that are not typically representative of theactive silicon area of the manufactured circuit design for each chip ona wafer.

In various embodiments of the present invention, computing device 102 isa computing device that can be a stand-alone device, a server, a laptopcomputer, a tablet computer, a netbook computer, a personal computer(PC), or a desktop computer. In another embodiment, computing device 102represents a computing system utilizing clustered computers andcomponents to act as a single pool of seamless resources. In general,computing device 102 can be any computing device or a combination ofdevices with access to reliability program 110, database 112,semiconductor device 104, and tester 106, and is capable of executingreliability program 110. Computing device 102 may include internal andexternal hardware components, as depicted and described in furtherdetail with respect to FIG. 4.

Network 108 can be, for example, a local area network (LAN), a wide areanetwork (WAN) such as the Internet, or a combination of the two, and caninclude wired, wireless, or fiber optic connections. In general, network108 can be any combination of connections and protocols that willsupport communications between computing device 102, semiconductordevice 104 and tester 106.

Reliability program 110 resides on computing device 102. In anotherembodiment, reliability program 110 may reside on tester 106. In yetanother embodiment, reliability program 110 may reside in EQM controller124. Reliability program 110 draws data from database 112 to calculatethe predicted reliability of semiconductor device 104. According to anillustrative embodiment, reliability program 110 uses electricalcharacteristics detected by semiconductor device 104 to calculatephysical characteristics, for example, gate oxide thickness. Failurerate modeling of semiconductor device 104 uses the calculated gate oxidethickness to predict the reliability of semiconductor device 104. Oneimplementation of reliability program 110 is described in further detailwith respect to FIG. 3.

Database 112 resides on computing device 102. In another embodiment,database 112 may reside on tester 106. In yet another embodimentdatabase 112 may reside in EQM controller 124. Database 112 stores thedata that is used, by reliability program 110, to model the reliabilityof semiconductor device 104. Examples of data stored in database 112include equivalent oxide thickness (EOT) sensor circuit data 140,manufacturing circuit data 132, application use conditions sensorcircuit data 134, as well as reliability model with product-specificconfidence bounds 136. EOT sensor circuit data 140 is leakage currentdata that was described above. EOT sensor circuit data 140 is used tocalculate the oxide thickness value that is used in reliabilitymodeling. Manufacturing circuit data 132 may include process variabilitydata and/or defect density data collected during the fabrication of thesemiconductor device. Manufacturing circuit data 132 is used to adaptthe reliability model with real-time, per-chip data. Application useconditions sensor circuit data 134 describes the environmentalconditions that a semiconductor device may be subjected to over the lifeof the device. Examples of application use conditions sensor circuitdata include system ambient temperature and power on hours. Reliabilitymodel with product-specific confidence bounds 136 includes a pluralityof algorithms for calculating estimated failure rate, includingalgorithms for calculating early life failure rate and intrinsic failurerate, based on the per-chip EOT measurements. Database 112 may alsoinclude screens and guard band data 138 that is used to generate testlimits for use by tester 106. Screens and guard band data 138 mayinclude data from a 3D part average test. Requirements for screens andguard band data 138 may be generated by translating the quality andreliability requirements of the semiconductor device into test criteria.

Semiconductor device 104 includes a plurality of components. For testpurposes, a component for boundary scan test known as JTAG (Joint TestAction Group) 122 is included. JTAG 122 may include a self-test functionknow as a built-in self test (BIST). In the present embodiment, JTAG 122interacts with Tester 106. Semiconductor device 104 also includes anembedded quality management component referred to as EQM controller 124.EQM controller 124 includes many different forms of interfaces,including control interface, JTAG interface, sensor interface, etc. Incertain embodiments, EQM controller 124 includes a centralizedprogramming interface and takes measurements, calculates EOT and adaptsthe reliability prediction for semiconductor device 104. In such a case,reliability program 110 and database 112 are contained withinsemiconductor device 104, and computing device 102 is not required inthe semiconductor testing environment.

In a first embodiment, semiconductor device 104 also includes scalableparametric macro (SPM) 126. SPM 126 provides power supplies, controlsignals, input and output signals to a family of circuit sensors (i.e.EOT, Temperature, Voltage, Power-on-Hours, etc.). SPM 126 also serves asthe interface to tester 106 and to EQM controller 124 during per-chipcircuit measurements and processing of the confidence bounds of theapplication-specific reliability model updates. Custom logic 130performs the intended function of the chip. For example, if the chip isan application specific integrated circuit (ASIC), custom logic 130performs the function for which the chip is designed. If, for example,the chip is designed to run a digital voice recorder or to control thefunctions of an automobile, then custom logic 130 performs thosefunctions.

In a first embodiment, SPM 126 is connected to a network of EOT sensorfamilies, referred to as sensor circuit families 128. Sensor circuitfamilies 128 reside in strategically designed areas of the siliconoccupied by custom logic 130 to provide sufficient spatial coverage tominimize on-chip variability.

In a first embodiment, sensor circuit families 128 include a family oftransistors with equivalent RLC (resistance, inductance, capacitance)models, a programmable network unit, and a programmable voltageregulation unit configured to measure a family of reliability modelparameters as a function of component functional operating performance.Sensor circuit families 128 detect leakage current through theintegrated circuit gate. Leakage refers to a gradual loss of energy froma charged capacitor. Typically, a large area planar capacitor, boundedeither by shallow trench isolation (STI) or diffusion, is used for thismeasurement because the average coverage over the planar surface areaenables good leakage measurements that are dependent on average oxidethickness and are not as affected by random variations. Reliabilityprogram 110 calculates the equivalent gate oxide thickness by insertingthe detected leakage current value into an industry standard formula foroxide thickness. In general, such a calculation takes into account thedetected leakage current and the area over which the leakage current wasmeasured, as well as several coefficients specific to the technologybeing tested, as known to one skilled in the art.

In a first embodiment, tester 106 is an apparatus used to testintegrated circuits, for example, a wafer prober. In general, waferprobers test for certain static faults in semiconductor devices, causedmainly by manufacturing problems, for example, shorts, opens, and logicerrors. Tester 106 applies a voltage to sensor circuit families 128 todetect a resultant current. In one embodiment, tester 106 provides theelectrical measurements used by reliability program 110 to calculatereliability predictions for semiconductor device 104. In anotherembodiment, tester 106 interfaces with JTAG 122 on semiconductor device104 to provide the electrical measurements used by EQM controller 124 tocalculate reliability predictions for semiconductor device 104.

FIG. 2 is a flow diagram illustrating an integrated process forassessing the reliability of a semiconductor device with improvedproduct-specific confidence bounds. The qualification plan defines thecircuits, tests and pass/fail criteria required to meet thequalification objectives of a technology and/or product (step 202). Thequalification plan includes a list of required hardware, i.e. integratedcircuit chips (block 204), along with defined tests that the hardware isto be subjected, and pass/fail criteria. An example of a qualificationtest is accelerated thermal cycling, where the chip is subjected tocycles of high and low temperatures and tested at specified intervals todetermine whether the chip is still functional. Subsequent toqualification testing, test data is reviewed to determine whether thetest hardware passed or failed the defined test criteria (decision block206).

If the test hardware fails the defined test criteria (fail branch,decision block 206), failures are analyzed for root cause, andcorrective actions are implemented (step 212). For example, if a failureis determined to be the result of a manufacturing defect, improvedprocess features and/or controls may be implemented to prevent thedefect from re-occurring. If the corrective actions are significant interms of the affect on the integrated circuit reliability, thequalification plan may be updated to include a re-population of one ormore tests of improved hardware.

If the test hardware passes the defined test criteria (pass branch,decision block 206), the reliability models are reviewed to determinewhether the test hardware, and the current and future manufacturingprocesses are consistent with the expectations for the productionhardware. Subsequent to the test hardware passing the defined testcriteria, the reliability models may require updating (decision block208). If the reliability models require updating (yes branch, decisionblock 208), the circuit and/or manufacturing process updates underchange control may be validated using a reliability monitor (step 214).

If the reliability models do not require updating (no branch, decisionblock 208), the production readiness phase begins, and reliabilityprogram 110, which enables scaling for chip failure rate with improvedconfidence bounds, is executed (step 210). Scaling is a method ofmapping the failure rate of applications relative to a baseline failurerate prediction for a reference technology or size. Inputs to thescaling for chip failure rate include design manual specifications(block 218) and data from database 112, including chip circuitmanufacturing data, screens and guard band data, application useconditions, model parameters and chip-specific EOT sensor circuit data(block 220).

FIG. 3 is a flowchart depicting operational steps of reliability program110 residing on computing device 102, in accordance with an embodimentof the present invention. As will be appreciated by one skilled in theart, the reliability of an integrated circuit depends on the timing ofthe occurrence of various failure mechanisms in the life of theintegrated circuit. There are many reliability models for failuremechanisms of integrated circuits. Several models depend on the gateoxide thickness for prediction of reliability. Examples of failuremechanism models that depend on the gate oxide thickness are BiasTemperature Instability (BTI), Time Dependent Dielectric Breakdown(TDDB) and frequency degradation. The gate oxide thickness may beobtained by means of a leakage current measurement. By obtaining gateoxide thickness by means of measuring leakage current per eachindividual semiconductor device, the reliability modeling is optimizedbecause the model is specific to the semiconductor device being testedinstead of a general model based on a small sample of qualificationdevices and/or limited measurements from production wafer kerfstructures.

Reliability program 110 measures electrical characteristics of theintegrated circuit (step 302). In this embodiment, reliability program110 measures leakage current through the integrated circuit gate once avoltage is applied. Reliability program 110 uses sensor circuit families128 to detect the current. Subsequent to measuring electricalcharacteristics, reliability program 110 determines physical attributesof the integrated circuit (step 304). In this embodiment, reliabilityprogram 110 determines the gate EOT of each sensor location onsemiconductor device 104. Reliability program 110 calculates the gateEOT by inserting the detected leakage current into an industry standardformula, known as quantum mechanical direct tunneling current density asa function of dielectric thickness at a fixed applied voltage. As willbe known by one skilled in the art, the formula includes severaltechnology-specific coefficients, as well as the area of the gatethrough which the leakage current is measured.

Subsequent to calculating the EOT, reliability program 110 models thefailure rate for semiconductor device 104 (step 306). As mentionedpreviously, several different models exist for predicting reliability ofan integrated circuit using the EOT. In one embodiment, reliabilityprogram 110 uses the Bias Temperature Instability (BTI) model, as knownto one skilled in the art, to predict the failure rate of semiconductordevice 104. In another embodiment, reliability program 110 uses the TimeDependent Dielectric Breakdown (TDDB) model, as known to one skilled inthe art, to predict the failure rate of semiconductor device 104. In yetanother embodiment, reliability program 110 uses the frequencydegradation model, as known to one skilled in the art, to predict thefailure rate of semiconductor device 104. In yet another embodiment,reliability program 110 may use a combination of one or more models topredict the failure rate of semiconductor device 104. Predictingreliability on a per chip basis significantly reduces the variability inthe prediction results, enabling sorting of chips. For example, if achip were predicted to have a longer life than others in the same lot,that chip could be used in a specific application that requires longerlife. If, for example, a chip were predicted to have a shorter life thanothers in the same lot, that chip could be either used in a specificapplication that does not require a long life, or it could be discarded.

FIG. 4 depicts a block diagram of components of computing device 102 inaccordance with an illustrative embodiment of the present invention. Itshould be appreciated that FIG. 4 provides only an illustration of oneimplementation and does not imply any limitations with regard to theenvironments in which different embodiments may be implemented. Manymodifications to the depicted environment may be made.

Computing device 102 includes communications fabric 402, which providescommunications between computer processor(s) 404, memory 406, persistentstorage 408, communications unit 410, and input/output (I/O)interface(s) 412. Communications fabric 402 can be implemented with anyarchitecture designed for passing data and/or control informationbetween processors (such as microprocessors, communications and networkprocessors, etc.), system memory, peripheral devices, and any otherhardware components within a system. For example, communications fabric402 can be implemented with one or more buses.

Memory 406 and persistent storage 408 are computer-readable storagemedia. In a first embodiment, memory 406 includes random access memory(RAM) 414 and cache memory 416. In general, memory 406 can include anysuitable volatile or non-volatile computer-readable storage media.

Reliability program 110 and database 112 are stored in persistentstorage 408 for execution and/or access by one or more of the respectivecomputer processors 404 via one or more memories of memory 406. In thisembodiment, persistent storage 408 includes a magnetic hard disk drive.Alternatively, or in addition to a magnetic hard disk drive, persistentstorage 408 can include a solid state hard drive, a semiconductorstorage device, read-only memory (ROM), erasable programmable read-onlymemory (EPROM), flash memory, or any other computer-readable storagemedia that is capable of storing program instructions or digitalinformation.

The media used by persistent storage 408 may also be removable. Forexample, a removable hard drive may be used for persistent storage 408.Other examples include optical and magnetic disks, thumb drives, andsmart cards that are inserted into a drive for transfer onto anothercomputer-readable storage medium that is also part of persistent storage408.

Communications unit 410, in these examples, provides for communicationswith other data processing systems or devices, including resources ofsemiconductor device 104 and tester 106. In these examples,communications unit 410 includes one or more network interface cards.Communications unit 410 may provide communications through the use ofeither or both physical and wireless communications links. Reliabilityprogram 110 and database 112 may be downloaded to persistent storage 408through communications unit 410.

I/O interface(s) 412 allows for input and output of data with otherdevices that may be connected to computing device 102. For example, I/Ointerface 412 may provide a connection to external devices 418 such as akeyboard, keypad, a touch screen, and/or some other suitable inputdevice. External devices 418 can also include portable computer-readablestorage media such as, for example, thumb drives, portable optical ormagnetic disks, and memory cards. Software and data used to practiceembodiments of the present invention, e.g., reliability program 110 anddatabase 112, can be stored on such portable computer-readable storagemedia and can be loaded onto persistent storage 408 via I/O interface(s)412. I/O interface(s) 412 also connect to a display 420.

Display 420 provides a mechanism to display data to a user and may be,for example, a computer monitor.

The programs described herein are identified based upon the applicationfor which they are implemented in a specific embodiment of theinvention. However, it should be appreciated that any particular programnomenclature herein is used merely for convenience, and thus theinvention should not be limited to use solely in any specificapplication identified and/or implied by such nomenclature.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which includes one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

Embodiments of the present invention may be used in a variety ofelectronic applications, including but not limited to advanced sensors,memory/data storage, semiconductors, microprocessors and otherapplications.

A resulting integrated circuit chip can be distributed by the fabricatorin raw wafer form (that is, as a single wafer that has multipleunpackaged chips), as a bare die, or in a packaged form. In the lattercase the chip is mounted in a single chip package (such as a plasticcarrier, with leads that are affixed to a motherboard or other higherlevel carrier) or in a multichip package (such as a ceramic carrier thathas either or both surface interconnections or buried interconnections).In any case the chip is then integrated with other chips, discretecircuit elements, and/or other signal processing devices as part ofeither (a) an intermediate product, such as a motherboard, or (b) an endproduct. The end product can be any product that includes integratedcircuit chips, ranging from toys and other low-end applications toadvanced computer products having a display, a keyboard or other inputdevice, and a central processor.

Having described the preferred embodiment of creating integratedcircuits that each include at least one per-chip EOT sensor (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations may be made by persons skilled in the artin light of the above teachings.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description. Areference to an element in the singular is not intended to mean “one andonly one” unless specifically stated, but rather “one or more.” Allstructural and functional equivalents to the elements of the variousembodiments described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and intended to be encompassed by theinvention. It is therefore to be understood that changes may be made inthe particular embodiments disclosed which are within the scope of thepresent invention as outlined by the appended claims.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer-readablemedium(s) having computer readable program code/instructions embodiedthereon.

Any combination of computer-readable media may be utilized.Computer-readable media may be a computer-readable signal medium or acomputer-readable storage medium. A computer-readable storage medium maybe, for example, but not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus, ordevice, or any suitable combination of the foregoing. More specificexamples (a non-exhaustive list) of a computer-readable storage mediumwould include the following: an electrical connection having one or morewires, a portable computer diskette, a hard disk, a random access memory(RAM), a read-only memory (ROM), an erasable programmable read-onlymemory (EPROM or Flash memory), an optical fiber, a portable compactdisc read-only memory (CD-ROM), an optical storage device, a magneticstorage device, or any suitable combination of the foregoing. In thecontext of this document, a computer-readable storage medium may be anytangible medium that can contain, or store a program for use by or inconnection with an instruction execution system, apparatus, or device.

A computer-readable signal medium may include a propagated data signalwith computer-readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer-readable signal medium may be any computer-readable medium thatis not a computer-readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer-readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java®, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on a user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in acomputer-readable medium that can direct a computer, other programmabledata processing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce acomputer-implemented process such that the instructions which execute onthe computer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

What is claimed is:
 1. A method for optimizing reliability of integratedcircuits, the method comprising: a computer integrating a per-chipequivalent oxide thickness (EOT) circuit sensor into an integratedcircuit, wherein the integrated circuit is included in a plurality ofintegrated circuit chips included in a semiconductor wafer, such thateach integrated circuit chip includes one or more per-chip equivalentoxide thickness (EOT) circuit sensor(s) the computer utilizing theper-chip EOT circuit sensor to determine electrical characteristics ofthe integrated circuit; and the computer determining physical attributesof the integrated circuit as a function of the determined electricalcharacteristics.
 2. The method of claim 1, wherein determiningelectrical characteristics comprises utilizing an external testapparatus to apply a voltage to the per-chip EOT circuit sensor and todetect a resultant leakage current.
 3. The method of claim 1, whereindetermining electrical characteristics comprises utilizing Joint TestAction Group (JTAG) self-test functions embedded in the integratedcircuit to apply a voltage to the per-chip EOT circuit sensor and todetect a resultant leakage current.
 4. The method of claim 1, whereindetermining physical attributes comprises utilizing the determinedelectrical characteristics to calculate equivalent oxide thickness. 5.The method of claim 4, wherein utilizing the determined electricalcharacteristics comprises inserting a detected value of leakage currentinto an algorithm for calculating equivalent oxide thickness.
 6. Themethod of claim 1, further comprising the step of: the computer modelinga predicted integrated circuit failure rate using the determinedphysical attributes of the integrated circuit.
 7. The method of claim 6,wherein modeling a predicted integrated circuit failure rate comprisesthe steps of: the computer inserting the determined physical attributesin at least one of a plurality of reliability prediction algorithms; andthe computer calculating the predicted integrated circuit failure rateper chip included in a plurality of integrated circuit chips.
 8. Acomputer program product for optimizing reliability of integratedcircuits, the computer program product comprising: one or morecomputer-readable storage media and program instructions stored on theone or more computer-readable storage media, the program instructionscomprising: program instructions to utilize a per-chip equivalent oxidethickness (EOT) circuit sensor to determine electrical characteristicsof an integrated circuit wherein the integrated circuit is included in aplurality of integrated circuit chips included in a semiconductor wafer,wherein each integrated circuit chip includes one or more per-chip EOTcircuit sensor(s); and program instructions to determine physicalattributes of the integrated circuit as a function of the determinedelectrical characteristics.
 9. The computer program product of claim 8,further comprising: program instructions to determine electricalcharacteristics of the integrated circuit utilizing an external testapparatus to apply a voltage to the per-chip EOT circuit sensor and todetect a resultant leakage current.
 10. The computer program product ofclaim 8, further comprising: program instructions to determineelectrical characteristics utilizing self-test functions embedded in theintegrated circuit to apply a voltage to the per-chip EOT circuit sensorand to detect a resultant leakage current.
 11. The computer programproduct of claim 8, further comprising: program instructions todetermine physical attributes of the integrated circuit utilizing thedetermined electrical characteristics.
 12. The computer program productof claim 8, further comprising: program instructions to insert adetected value of leakage current into an algorithm for calculatingequivalent oxide thickness.
 13. The computer program product of claim 8,further comprising: program instructions to model a predicted integratedcircuit failure rate using the determined physical attributes of theintegrated circuit.
 14. The computer program product of claim 13,further comprising: program instructions to insert the determinedphysical attributes into at least one of a plurality of reliabilityprediction algorithms, and thereby calculate the predicted integratedcircuit failure rate.
 15. A semiconductor wafer structure, the structurecomprising: a plurality of integrated circuit chips included in asemiconductor wafer, wherein each chip includes one or more per-chipequivalent oxide thickness (EOT) circuit sensor; wherein each EOTcircuit sensor is configured to determine electrical characteristics ofthe integrated circuit; and wherein physical attributes of theintegrated circuit are determined using the determined electricalcharacteristics.
 16. The structure of claim 15, the structure furthercomprising an external test apparatus that applies a voltage to theper-chip EOT circuit sensor and detects a resultant leakage current todetermine an electrical characteristic of the plurality of integratedcircuit chips.
 17. The structure of claim 16, the structure furthercomprising a plurality of electrical connections that connect the EOTcircuit sensors to the test apparatus such that the EOT circuit sensorsare in electrical contact with the test apparatus and can pass data thatindicate electrical characteristics of a given integrated circuit. 18.The structure of claim 15, the structure further comprising Joint TestAction Group (JTAG) self-test structures embedded in the integratedcircuit that applies a voltage to the per-chip EOT circuit sensor anddetects a resultant leakage current to determine an electricalcharacteristic of the plurality of integrated circuit chips.
 19. Thestructure of claim 18, the structure further comprising a plurality ofconnections that connect the EOT circuit sensors to the JTAG self-teststructures such that the EOT circuit sensors are in electrical contactwith the JTAG self-test structures and can pass data that indicateselectrical characteristics of a given integrated circuit.
 20. Thestructure of claim 15, wherein the EOT circuit sensors comprise one ormore of a family of transistors with equivalent RLC (resistance,inductance, capacitance) models, a programmable network unit, and aprogrammable voltage regulation unit.